Map Block: Fix the Map Theme selector style in Gutenberg 6.7+

[pento]

WordPress/gutenberg#17880 landed in Gutenberg 6.7, which changed a class name that the Map block depended on for the Map Theme selector.

Fixes #14058.

Changes proposed in this Pull Request:

Add an additional class selector to the Map Theme CSS, so that it will work with the block editor in WordPress Core, and Gutenberg.

Is this a new feature or does it add/remove features to an existing part of Jetpack?

Bug fix.

Testing instructions:

• Install and activate the Gutenberg plugin.
• Add a Map block.
• Check that the Map Theme options show the mini preview images.
• Confirm that it appears the same when the Gutenberg plugin is deactivated.

Screenshots:

Before

After

Proposed changelog entry for your changes:

• Map Block: Fixed display of the Map Theme selector in Gutenberg 6.7+.

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello pento! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer, review, and approve D35637-code before merging this PR. Thank you!

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: November 19, 2019.
Scheduled code freeze: November 12, 2019

Generated by 🚫 dangerJS against 1160a04

[jeherve]

It seems to work well for me. 👍